The embodiments of the present invention relate generally to methods and apparatus for hydraulically coupling two components. More particularly, the embodiments provide a hydraulic coupler that shifts the supply of hydraulic fluid from a first source to a second source and prevents external fluid pressure from entering the hydraulic fluid paths. Still more particularly, the embodiments of the present invention relate to hydraulic couplers for subsea equipment, such as hydraulic couplers integrated into a tubing hanger that allow selection between hydraulic control from a running tool and hydraulic control from a subsea christmas tree.
In performing a well completion, a tubing hanger supporting a tubing string and downhole control members is placed within a well and landed on a wellhead member, such as a subsea Christmas tree. Hydraulic control lines extend from the tubing hanger to selected downhole control members, such as a downhole safety valve or a downhole chemical injection member, for actuation and control of the downhole control members. Hydraulic control fluid passages in the wellhead member and the tubing hanger are aligned in the landed position of the tubing hanger for the supply of the hydraulic control fluid from the wellhead member through the tubing hanger to downhole control members.
To move the tubing hanger to the wellhead, the hanger is releasably connected to a running tool and lowered through a riser connected to the well. The running tool is disconnected from the tubing hanger after landing of the tubing hanger on the wellhead member and hydraulic connectivity has been established between the tubing hanger and the wellhead member. It is often desirable that hydraulic control fluid be supplied, or have the capability of being supplied, to certain downhole control members before the tubing hanger is landed on the wellhead member and under control of the subsea wellhead member. In order to facilitate this control, hydraulic control fluid circuitry extends through a running tool for the supply of hydraulic control fluid to the tubing hanger and the downhole control members and the tubing hanger is constructed so as to receive hydraulic signals from the running tool.
Thus, because it is desirable to have the downhole control members under positive hydraulic control at all times, at least two alternate hydraulic fluid paths are required for each control line, a first path from the running tool and a second path for connection to the wellhead member. During the installation of the tubing hanger, the first hydraulic fluid path from the running tool is engaged and in use but the second hydraulic fluid path is left accessible so as to facilitate subsea connection to the wellhead member. Although the second hydraulic fluid path must be able to be connected to the wellhead member, it should also be protected from the ingress of external fluids, such as fluids in the riser, that may tend to contaminate the hydraulic system or interfere with proper operation of the downhole control members. The ingress of drilling fluids from the riser is of particular concern when the drilling fluid has a much higher density or is at a higher pressure than the hydraulic fluid in the tubing hanger and running tool.
Therefore, it is desirable to have a system that shifts the supply of hydraulic fluid to the tubing hanger from the running tool to the wellhead member and isolates the non-active hydraulic fluid path in order to prevent contamination or interference with the desired hydraulic communication. Therefore, the embodiments of the present invention are directed to methods and apparatus for providing for the selection between two hydraulic fluid supplies while protecting the hydraulic system from contamination that seek to overcome the limitations of the prior art.